1. Field of the Invention
The invention is of percutaneous implants of enhanced biocompatibility, blood compatibility, and corrosion resistance. More specifically, the invention implants are fabricated from relatively low modulus metals, such as zirconium or a zirconium-containing alloy, and are coated with blue to black zirconium oxide or zirconium nitride to provide enhanced blood compatibility, microfretting resistance, electrical insulation, and corrosion resistance where applicable.
2. Description of the Related Art
With advances in the technology for treating heart diseases, there has developed an increasing demand for sophisticated cardiovascular implants and surgical tools for use in cardiovascular surgery.
Certain cardiac treatment procedures require the use of pacemaker leads and other current-bearing leads that are usually coated with an insulative barrier that both electrically insulates and isolates the current-bearing core from body fluids. Currently, a typical pacemaker or other cardiovascular lead includes a central core of electrically conductive metal, usually cobalt-nickel alloy, coated with a polymeric insulative coating, usually polyurethane. However, polyurethane coatings eventually break down under the effect of body fluids and enzymes producing potentially harmful degradation products. Further, the polymer coating may crack or separate with time so that body fluids or adjacent wires come in contact with the electrical conductor and interfere with electrical signals. Further, the electrical conductor is then subject to corrosion due to body fluids.
In a typical defibrillator, a flexible silicone polymeric patch with a thinly coiled titanium, cobalt-nickel, or stainless steel wire is attached to the appropriate segment of heart muscle. A lead wire is attached to this coil for powering the coil to stimulate the heart muscle. The lead wire exits from the body to an external power source. The lead wire is frequently coated with polyurethane. Thus, this lead wire is both an electrical carrying device and a percutaneous device, in the sense that it penetrates the skin and exits from the body. However, it is coated with a relatively soft and fragile polymeric composition which provides limited protection to potential damage to lead sections carried outside the body. Thus, there is a need for a percutaneous lead that is crush resistant, biocompatible, and that provides suitable electrical conductance and insulation to isolate the electrical carrying lead from other lead wires and body tissue. Further, the lead should be resistant to chemical degradation in body fluids.